1. Technical Field
This invention relates generally to the field of lithography and, more particularly, to approaches for enhancing resolution in lithographic processes using high refractive index fluids (e.g., in immersion lithography).
2. Related Art
Optical proximity correction (OPC) is a photolithography enhancement technique commonly used to compensate for image errors due to diffraction or process effects. A need for OPC is seen mainly in the making of semiconductor devices and is due to the limitations of light to maintain edge placement integrity of an original design, after processing, into the etched image on the silicon wafer. Specifically, projected images often appear with irregularities such as line widths that are narrower or wider than designed. Other distortions such as rounded corners are driven by the resolution of the optical imaging tool and are harder to correct. OPC corrects these errors by moving edges or adding extra polygons to a pattern written on a photomask. This may be accomplished using pre-computed look-up tables based on width and spacing between features (known as rule-based OPC), or by using compact models to dynamically simulate the final pattern, and thereby drive the movement of edges to find the best solution (this is known as model-based OPC). For current mask generation, a POR standard fragmentation scheme is typically utilized for lithographic fills. The drawbacks of a POR process is that when used by lithographic fills, POR techniques increase OPC runtime, and adversely impact mask-write times.